Bismuth-based heterometallic clusters capped by thiacalixarene for visible-light photothermal conversion

Abstract

Two isostructural heterometallic coordination clusters, [BiM₂(HTC4A)₂(CH₃COO)]₂ (+solvents) (Bi₂M₄, M = Co or Ni, H₄TC4A = p-tert-butylthiacalix[4]arene), were synthesised under solvothermal conditions and structurally characterised by single-crystal X-ray diffraction. The Bi₂M₄ clusters exhibited double-dumbbell molecular structures, wherein each BiM₂ cluster is interposed between two calixarenes and bridged by two acetate groups. Bi₂Co₄ and Bi₂Ni₄ demonstrated light-to-heat conversion capabilities in both solid-state and organic solvents while exhibiting distinct electron transfer pathways. The mechanism of light-driven hot electron transfer in photothermal conversion was elucidated by integrating visible-light photothermal conversion efficiency assessments, DFT calculations, and XPS measurements, which collectively highlighted the predominant role of Bi-S/M-S coordination with calixarenes.